Separation of acetone and propionaldehyde by azeotropic distillation with chloroform



Aug. 18, 1953 J. M. HARRISON ET AL 2,649,406

' SEPARATION OF ACETONE AND PROPIONALDEHYDE BY A zEoTRoIc DISTILLATIONWITH cHLoRoFoRM Filed March 14, 1952 Patented Aug. 18, 1953 UNITEDSTATES ATENT GFFICE SEPARATION OF ACETONE AND PROPION- ALDEHYDE BYAZEOTROPIC DISTILLA- TION WITH CHLOROFORM Application March 14, 1952,Serial No. 276,614

4 Claims. (Cl. 202-4Z) This invention relates to a process of separatingorganic compounds and more particularly to a process of separating amixture of acetone and propionaldehyde.

Mixtures `of acetone and propionaldehyde are obtained in the oxygenatedproducts from the Fischer-Tropsch synthesis and from the oxidation oflow-molecular weight hydrocarbons, such as natural gas. These may occuras aqueous or nonaqueous mixtures. It is desirable to separate theaqueous or nonaqueous mixture and obtain acetone and propionaldehyde asproducts. It is difficult to obtain a sharp separation by distillationbetween acetone and propionaldehyde because they boil within a narrowrange.

We have found that a mixture of acetone, propionaldehyde and water scanbe separated by first stripping acetone and propionaldehyde from themixture and then passing the mixture of acetone and propionaldehyde to adistillation zone, adding chloroform to theA distillation zone, removingpropionaldehyde as overhead and discharging it as product, and removingas bottoms a mixture containing the azeotropc amounts of about 20 weightper cent acetone and 80 weight per cent chloroform.

The mixture of acetone and chloroform is then further separated. This ispreferably accomplished by passing the mixture of azeotropic compositionto an extraction zone, adding water, preferably from five to ten volumesof water per volume of the mixture of chloroform and acetone, to theextraction zone, removing a raffinate phase containing acetone andchloroform from the bottom of the extraction Zone, passing the rafnatephase to a second distillation zone, removing chloroform as overhead andamixture containing the azeotropic amounts of about 20 per cent acetoneand 80 per cent chloroform as bottoms from the second distillation zonewhile the extract phase .containing water and acetone is passed from thetop of the extraction zone to a second stripping zone where acetone isremoved overhead and water is removed as bottoms. Preferably thechloroform removed overhead from the second distillation zone isrecycled to the first distillation zone and the mixture containingazeotropic amounts of about 20 per cent acetone and 80 per centchloroform is recycled to the extraction zone.

The process of our invention is advantageous because it furnishes anefficient method for separating a mixture of acetone andpropionaldehyde. As was pointed out previously these compounds boilWithin a narrow range, propionaldehyde boiling at 48.8 C. at 760 mm. ofHg and acetone boiling at 56.2 C. at the same pressure. When chloroformis added to this mixture in the azeotropic amount with acetone, the nextmost volatile constituent in the system after propionaldehyde is themaximum boiling azeotrope of chloroform and acetone containing about 20per cent acetone and'about 80 per cent choloroform. This mixture boilsat 64.4 C. at '760 mm. of I-Ig. Thus, the addition of chloroformincreases the difference in boiling points between the components to beseparated from 7.4 C. to 15.6 C.

The separation of a mixture of acetone and chloroform of azeotropiccomposition in an extraction zone with water is also eiiiciently ac'-complished. We have found that in a one-stage extraction at roomtemperature with about five to ten volumes of water per volume ofmixture of chloroform and acetone, an extract is obtained free ofchloroform and a raffinate is obtained free of water.

The process of Iour inventioncan be understood more fully by referenceto the accompanying drawing, the single gure of which shows adiagrammatical layout of apparatus which will be described inconjunction with an embodiment of our invention.

Referring to the drawing, a mixture of acetone, propionaldehyde andWater is passed by line 5 containing valve 6 into stripping stil-1 l.Water is removed as bottoms .from stripping still I by line 8 containingvalve 9 and is discharged from the system. A mixture of acetone andpropionaldehyde is removed overhead from stripping still I by line I0containing valve I I and is passed by line I0 to line I4. v

The mixture of acetone and propionaldehyde in line I4 is introduced intodistillation still I5. Chloroform is passed into distillation still I5by line I6 containing valve I'I. This still, in the present embodiment,is operated at about atmospheric pressure and so that the temperature ofthe overhead vapors is about 50 to about 55 C. The rate of addition ofchloroform is adj-usted so that sufficient chloroform is present at alltimes to form a mixture containing the azeotropic amounts of about 20weight per cent acetone and about 80 per cent chloroform.Propionaldehyde is removed overhead from still I5 by line I8 containingvalve I9 and is discharged as product. A mixture containing theazeotropic amounts of about 20 Weight per cent acetone and about 80weight per centl chloroform is removed as bottoms from still' I5 by line20 containing valve 2| and is passed into extraction column 22. It isgenerally desirable to carry out the process with a small excess ofchloroform which is removed from the still with the mixture of acetoneand chloroform containing the azeotropic amounts of about Weight percent acetone and about 80 per cent chloroform. Water is admitted toextraction column 22 by line 23 containing valve 24. An extract mixturecontaining water and acetone is removed overhead fromv extraction column22 by line 25 containingV valve 25', and a mix-- ture of acetone andchloroform is removedas raffinate from the bottom of extraction. column22 by line 21 containing valve 28h.

The mixture of acetone and. chloroform ijs passed by line 21 intoconcentration still 29a. A mixture of acetone and chloroform containing.the azeotropic amount of about 2O Weight per cent acetone and about 8OWeight per cent'ohloroform is removed as bottoms from concentrationstill 29 by line 30 containing valve 3l and; is recycled by line 2t toextraction column. 22.. Chlo.- rofcrm in excess of the azeotropic amountis removed overhead rom concentration still 29 by line 32 containingvalve 33 and is recycled byline IG into distillation still I5.

The extract phase containing water and acetone removed from the top ofextraction column 22 by line 25 is passed into stripping still 34.Acetone is removed overhead from stripping still 3.4 by line 35containing valve 35and isdischarged as product. Water is removed fromthe bottom of stripping still 313 and is recycled by line 31 containingvalve 38. toline.- 23 and then to extraction column 22'. A portion. ofthe water may be discharged by line 39 containing valve El When it. isAdesired to reduce the amount of water introduced into extraction column212.

Some mixtures of acetone and propionaldehyde obtained, inA commercialoperationsA do not contain water in admixture with thev other materials.Where it is desired to treat only such a nonaqueous mixture, thestripping; still` l' need not be used and theA acetone-propionaldehydemixture is introduced intoy the system through line 4I having valve c2.Moreover, both aqueous and nonaqueous mixtures can be'separated usingequipment as shown in the drawing.; the. aqueous mixture. being passedthrough the stripping still l and the nonaqueous mixture beingintroduced through line. ll I.

An example of the operation of the process, of our invention will newVbe-described. A, mixture containing parts acetone; 20 parts,propionaldehyde, and 220 partswater is charged. into n stripping still'1. 220 parts of water are discharged as bottoms through line 81Amixture o f 50 parts acetone andr20.- parts propionaldehyde is removed.overhead byV line Il). and is combined in line I4 with a mixturecontaining 1.10. parts acetone and 70. parts propionaldehyde introducedby line 4I. The resulting mixture of 160.- parts acetone and 90 partspropionaldehyde is charged into azeotropic distillation stilll I5. 640parts' of chloroform recycled as` described belowV are introduced intodistillation Still I5.l by line I6.. 90 parts propionaldehyde areremoved overhead by line I8 and are discharged as product. A mixturecontaining 640 parts. of' chloroform and 160 parts of acetone is removedfrom distillation still I5 by line 29, and is combined with a mixturecontaining 360 parts chloroform and 90 parts acetone, recycled asdescribed below, by line 3u. The resulting mixture. containing. 1000parts chloroform and 250 parts acetone is introduced. into. extrac- Yremoved from extraction column 22 and is passed by line 21 intoconcentration still 29. 640 parts of chloroform are removed overheadfrom concentration Still 29 and are recycled by lines 32 and I6 toazeotropic distillation still I5. A mixture contain-ing the azeotropicamounts of 360 parts chloroform. and parts acetone is removed as'.bottoms from concentration still 29 and is passed by lines 3)- and 20 toextraction column 22.

The extract phase containing '7100 parts of Water and parts of acetoneis passed into stripping column 34. 160 parts of acetone are removedoverhead as product by line 35 and 7100 parts of Water are removed asbottoms and recycled to extraction column 22- by lines 3l and'23'.

An embodiment of our invention can be carried out as a batch process. Asan example of such an embodiment, a mixture containing 56.5 Weight percent chloroform 29 per cent propienaldehydc and 14.5 per cent acetone ischarged to a glass column, four feet long and oneY inch in diameter,packed with stainless steel carding teeth. and having about 35theoretical plates. They operating reflux ratio is adjusted. to about10:1. Propionaldehyde is removed first' at a temperaturel of 48.8 C. at760 mm. of Hg andthe chloroform*- acetone constant boiling mixtureisthen removed at about 64.4 C. The chloroform-acetoneeonstant boilingmixture is then extracted with water in the manner previously described.

Obviously many modifications and variations of the invention ashereinbefore set forth may be made without departing from the-spiritandA scope thereof and thereforeonly such limitations should be imposedas are indicated in the appended claims.

We. claim-z l. A process which comprises adding chloro,- form to amixture of acetone and propionaldehyde, distilling the resulting mixtureof' acetone, propionaldehyde and. chloroform, removing propionaldehyde.overhead as produca and removing as bottoms a mixture containingazeotropic amountsy of acetone and chloroform.

2. A process Which. comprises adding chloroformv to a mixture of;acetone and propionaldehyde in an amount at least equivalent to. thatre-` quired to form a mixture containing the` acectropieamounts of about20- Weight per cent-ace;- tone. and about 80 Weight Der. cent`chloroform', distilling the resultingv mixture of: acetone.. pro.-pioi-ialdehyde,l and chloroform, removing propicia.- aldehyde overheadas product, removing as bottoms a mixture containing the: azeotropicamounts of about 20 weight per centfacetcne and about. 80 Weight percent chloroform, and separating' acetone as product from said mixture ofchloroform and acetone.

3. A process of separating a mixture of acetone and propionaldehydewhich comprises adding chloroform to said mixture of acetone andpropionaldehyde in an amount at least equivalent to that required toform a mixture containing the azeotropic amounts of about 2u weightV percent acetone and about 80 Weight per cent chloroform, distilling theresulting mixture of acetone. proponaldehyde, and chloroform, in afirstv distillation zone, removing. propionaldehyde as @velhead and amixture containing the azeotropic amounts of about 20 Weight per centacetone and about 80 weight per cent chloroform as bottoms from said rstdistillation Zone, extracting said mixture of acetone and chloroform orazeotropic composition with Water in an extraction zone to form anextract mixture of acetone and Water and a rainate mixture of acetoneand chloroform, separating acetone as product from the extract mixture,distilling the rafnate mixture of chloroform and acetone in a seconddistillation zone to remove chloroform overhead and said mixture ofacetone and chloroform of azeotropic composition as bottoms, andrecycling said mixture of acetone and chloroform of azeotropiccornposition to said extraction zone.

4. A process of separating a mixture of acetone, propionaldehyde andWater which comprises removing Water from said mixture of acetone,propionaldehyde and water by distillation in a rst distillation zone,adding chloroform to the overhead mixture of acetone and propionaldehydefrom the first distillation zone in an amount at least equivalent tothat required to form a mixture containing the azeotropic amounts ofabout 20 weight per cent acetone and about 80 Weight per centchloroform, distilling the resulting mixture of acetone, propionaldehydeand chloroform in a second distillation zone, removing propionaldehydeas overhead at a temperature below 64.6 C. at 760 mm. of Hg and amixture containing the azeotropic amounts of about 20 weight per centacetone and 80 Weight per cent chloroform from said second distillationzone, extracting said mixture of acetone and chloroform with about 5 toabout 10 volumes of water in an extraction zone to form an extractmixture of Water and acetone and a raiiinate mixture of acetone andchloroform, passing the extract mixture of acetone and water to a thirddistillation zone, separating acetone overhead as product and recyclingWater as bottoms from the third distillation zone to the extractionzone, distilling the rainate mixture of acetone and chloroform in afourth distillation zone to remove chloroform overhead at a temperaturebelow 64.4 C. at 760 mm. of Hg and a mixture of acetone and chloroformof azeotropic composition as bottoms from the fourth Idistillation zone,and recycling said mixture of acetone and chloroform of azeotropiccomposition to the extraction zone.

JAMES M. HARRISON.

ALLEN E. SOMERS.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Jour. Am. Chem. Soc., Sept. 2475-2478.

Horsley, Tables of Azeotropic Data, Analytical Chemistry, vol. 19,August 1947, page 515.

1941, pages

1. A PROCESS WHICH COMPRISES ADDING CHLOROFORM TO A MIXTURE OF ACETONEAND PROPIONALDEHYDE, DISTILLING THE RESULTING MIXTURE OF ACETONE,PROPIONALDEHYDE AND CHLOROFORM, REMOVING PROPIONALDEHYDE OVERHEAD ASPRODUCT, AND REMOVING AS BOTTOMS A MIXTURE CONTAINING AZEOTROPIC AMOUNTSOF ACETONE AND CHLOROFORM.